/*
 * Copyright (c) 2015 Typelevel
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package cats
package instances

import scala.annotation.tailrec

trait ShowInstances {
  implicit def catsDeferForShow: Defer[Show] = ShowInstances.catsDeferForShowCache
}
object ShowInstances {
  private val catsDeferForShowCache: Defer[Show] =
    new Defer[Show] {
      case class Deferred[A](fa: () => Show[A]) extends Show[A] {
        private lazy val resolved: Show[A] = {
          @tailrec
          def loop(f: () => Show[A]): Show[A] =
            f() match {
              case Deferred(f) => loop(f)
              case next        => next
            }

          loop(fa)
        }
        override def show(t: A): String = resolved.show(t)
      }

      override def defer[A](fa: => Show[A]): Show[A] = {
        lazy val cachedFa = fa
        Deferred(() => cachedFa)
      }
    }
}
